UNIVERSITY  OF  CALIFORNIA  Agricultural  Experiment  Station 

College  of  agriculture  e.  j.  wickson,  acting  director 

BERKELEY,   CALIFORNIA 


CIRCULAR  No.  25 

(September,  1906.) 


SUGGESTIONS  REGARDING  THE  EXAMINATION  OF  LANDS 


BY 

E.  W.  HILGAKD. 


The  frequency  with  which  this  Station  is  called  upon  to  give  advice 
in  regard  to  soils,  whether  in  respect  to  the  quality  and  best  adaptations 
of  new  lands,  or  the  correction  of  faults  observed  in  those  already  under 
cultivation,  renders  it  desirable  to  formulate  some  general  explanations 
on  the  subject,  which  may  in  many  cases  enable  the  farmer  to  come  to  a 
definite  forecast  or  conclusion,  without  individual  consultation  and  ad- 
vice; or,  when  this  is  not  attainable,  may  so  instruct  him  that  he  can 
forward  to  the  Station  such  definite  statements  of  facts,  and  samples 
properly  taken,  as  will  convey  the  data  needful  for  a  full  understanding 
of  the  situation. 

Very  many  conditions  contribute  toward  the  agricultural  character- 
istics of  a  soil,  and  any  one  or  more  of  these  may,  under  certain  circum- 
stances, be  the  controlling  one.  It  is  therefore  essential  that  the  infor- 
mation given  by  the  farmer  should  be  as  complete  as  possible,  since  with- 
out it  the  trouble  involved  in  the  examination  of  samples  will  as  a  rule 
not  be  justified,  as  lacking  the  proper  basis  for  an  intelligent  opinion  or 
fruitful  advice. 

Not  many  years  ago  it  was  the  custom  to  ascribe  the  languishing  or 
death  of  trees  and  crops  to  some  "poison"  contained  or  generated  in  the 
soil.  In  California,  the  poison  theory  still  maintains  itself  to  some  extent, 
in  ascribing  the  trouble  observed  to  "alkali,"  even  though  no  manifes- 
tations of  that  substance  may  ever  appear  on  the  surface.  But  unless  a 
soil  at  the  end  of  the  dry  season  shows  a  white  crust  or  dust  of  alkali 
salts  on  the  surface,  there  is  no  reason  whatever  to  suppose  that  alkali  has 
anything  to  do,  directly,  with  injury  to  the  crop  or  trees;  for  such  injury  is 
rarely  done  to  the  roots  in  the  soil,  but  usually  by  the  accumulation  of 
alkali  salts  near  the  surface. 

Leaving  aside  the  case  of  special  diseases,  such  as  are  due  to  the 
action  of  fungi,  insects,  or  other  organisms,  it  has  now  become  usual,  in 
this  State  at  least,  to  attribute  any  faulty  or  defective  growth  of  culture 
plants  to  some  chemical  defect  in  the  soil,  and  to  address  to  the  Station 
the  question  what  fertilizer  should  be  used  to  make  up  the  deficiency. 


Extended  investigation  of  our  soils  has  shown  that  in  California,  far 
more  than  in  the  Eastern  States,  very  few  soil-materials  exist  that  would 
not  naturally  produce  good  crops  for  some  18  or  20  years  without 
fertilization,  provided  they  are  of  sufficient  depth  and  are  adequately 
supplied  with  moisture.  In  many  cases,  forty  or  fifty  years  is  a  low  esti- 
mate for  the  duration  of  profitable  production.  When,  therefore,  in  orch- 
ard or  vineyard,  it  is  noticed  that  after  growing  well  from  three  to  five 
years,  or  even  longer,  the  trees  or  vines  begin  to  languish,  and  sometimes 
even  to  die,  it  is  not  as  a  rule  reasonable  to  conclude  that  it  is  for  want 
of  any  needful  ingredient  in  the  soil.  This  is  especially  true  of  the  "die- 
back"  in  orchards — the  dying  of  the  tips  of  branches  in  the  tree-tops, 
which,  when  not  clearly  due  to  scale  insects  or  fungous  attack,  is  nearly 
always  caused  by  some  defect  in  the  subsoil,  at  or  near  the  ends  of  the 
roots;  such  as  hardpan,  dry  gravel  layers,  bottom  water,  or  the  like.  Such 
defects  cannot,  of  course,  be  cured  by  fertilization;  and  the  farmer  him- 
self can,  by  the  exercise  of  common  sense  and  digging  to  the  ends  of  the 
roots,  satisfy  himself  very  quickly  of  the  existence  or  absence  of  such 
defects,  which  can  often  not  be  recognized  when  samples  are  sent  to  the 
Station,  but  must  be  observed  on  the  spot. 

Importance  of  the  Subsoil. — In  our  dry  climate,  depth  of  the  soil  is  of 
the  first  importance,  since  the  roots  of  culture  plants  must  go  deep  in 
order  to  be  secure  against  the  summer's  drought.  As  the  latter  renders 
the  surface  soil,  which  in  the  humid  region  is  the  main  source  of  supply 
to  plants,  practically  unavailable  during  a  large  part  of  the  season  of 
growth,  it  is  clear  that  here,  more  than  anywhere,  the  depth  and  qaulity 
of  the  subsoil  is  of  the  greatest  importance,  and  should  be  investigated  in 
all  cases  by  the  intending  purchaser  of  land  before  investing.  The  omis- 
sion of  this  simple  precaution  has  led  to  untold  losses  and  disappoint- 
ments, which  have  been  the  more  frequent  as  the  formation  of  a  "hard- 
pan"  at  a  depth  corresponding  more  or  less  to  the  penetration  of  the 
annual  rainfall,  is  of  unusually  frequent  occurrence  in  this  State.  The 
richest  surface  soil  may  be  utterly  useless  for  general  farming  purposes 
if  underlaid,  at  a  depth  varying,  according  to  the  nature  of  the  soil,  from 
one  to  four  feet,  by  a  hardpan  or  clay  impervious  to  the  roots  of  plants. 
As  a  rule  it  is  not  practically  feasible  to  maintain,  even  by  irrigation,  a 
proper  supply  of  moisture  in  a  light  soil  limited  in  depth  by  impervious 
hardpan  at  two  or  three  feet,  even  in  cases  where  the  roots  of  the  crop 
do  not  habitually  penetrate  beyond  that  depth;  in  the  case  of  fruit  trees 
and  vines  (the  roots  of  which  in  certain  lands  are  limited  only  by  a  depth 
beyond  fifteen  or  twenty  feet)  the  objection  to  such  lands  in  their  nat- 
ural condition  is  insuperable,  unless  the  difficulty  can  be  overcome  by 
dynamiting  the  tree-holes. 

An  equally  fatal  objection,  so  far  as  tree  culture  is  concerned,  lies 
against  too  close  proximity  of  bottom  water  to  the  surface.  The  roots 
of  culture  plants  will  bear  submergence  only  for  a  very  limited  time  with- 
out injury  (forty  days  is  considered  the  extreme  limit  in  the  case  of  vines 
and  orchard  trees) ;  hence  lands  periodically  overflowed  and  not  very 
perfectly  drained  are  unsafe  for  the  planting  of  trees,  as  the  roots  will 
decay  where  the  air  is  excluded;   and  such  injured  roots  will  inevitably 


render  the  tree  unproductive,  if  they  do  not  kill  it  in  the  course  of  time. 
The  same  effects  are  of  course  produced  wherever  leaky  irrigation  ditches 
cause  the  rise  of  water  to  within  a  few  feet  of  the  surface.  Drainage, 
not  fertilization,  is  the  effective  remedy  in  such  cases.  Yet  such  lands 
may  be  well  adapted  to  the  growth  of  certain  shallow-rooted  crops,  par- 
ticularly of  those  having  a  short  period  of  growth. 

On  the  other  hand,  in  some  kinds  of  sandy  lands,  the  breaking  up  of 
what  might  be  considered  a  hardpan,  as  compared  with  the  surface  soil, 
may  almost  wholly  destroy  its  cultural  value  by  rendering  it  "leachy, ' ' 
so  that  neither  irrigation  water  nor  fertilizers  will  be  sufficiently  retained 
for  the  profitable  growth  of  crops.  It  is  therefore  clearly  necessary  that 
not  only  the  existence  of  such  underground  layers  be  definitely  ascer- 
tained, but  also  that  their  particular  nature  be  considered  with  respect 
to  the  kind  of  surface  soil,  and  to  the  practically  feasible  or  profitable 
uses  to  which  the  land  is  intended  to  be  put. 

Examination  of  the  Subsoil. — Outside  of  adobe  tracts,  an  exceedingly 
simple  and  effective  device  for  subsoil  examination  is  a  square  steel  rod 
not  less  than  a  quarter  of  an  inch  in  diameter,  well  pointed  at  one  end, 
and  provided  at  the  other  with  a  stout  iron  ring  for  the  reception  of  a 
cross-handle,  such  as  is  used  for  post-hole  augers.  With  such  a  prod  or 
sounding-rod,  not  less  than  five  feet  in  length,  and  made  to  penetrate  the 
soil  by  means  of  a  slight  reciprocating  motion  aided  by  the  weight  of 
the  operator,  the  exploration  of  the  subsoil  for  hardpan,  dense  clay  layers 
or  bottom  water  becomes  a  matter  of  a  few  minutes;  and  a  few  hours' 
time  suffices  to  thus  explore  extended  tracts,  and  perhaps  save  bad  in- 
vestments of  thousands  of  dollars;  or,  at  the  very  least,  to  convey  very 
valuable  information  as  to  the  probable  defects  or  virtues  of  the  land, 
not  only  with  respect  to  root  penetration,  but  also  with  regard  to  irriga- 
tion, drainage,  etc.  It  is  easy  also  to  detect  thus,  with  a  little  practice, 
the  presence  of  underlying  layers  of  quicksand,  gravel,  or  other  loose 
materials  through  which  irrigation  water  would  waste,  or  which  would 
present  the  capillary  rise  of  bottom  moisture  within  the  reach  of  plant 
roots,  by  the  large  iterspaces  between  their  grains.  Any  remaining 
doubts  as  to  the  nature  of  such  underlying  materials  at  particular  points 
can  then  quickly  be  settled  by  the  use  of  a  post-hole  auger.  The  latter 
serves  also  most  conveniently  for  the  taking  of  samples  to  be  submitted 
for  examination  by  the  Station;  but  it  should  be  remembered  that  in  no 
case  should  any  one  sample  represent  the  average  of  more  than  one  foot 
in  depth;  and  that  whenever  a  material  change  of  resistance  to  the 
auger's  penetration  is  observed,  the  depth  at  which  such  change  occurs 
should  be  noted,  and  a  sample  taken  of  the  material  causing  such  change, 
again  not  to  exceed  in  any  case  the  additional  depth  of  one  foot. 

The  extreme  depth  to  which  the  boring  and  taking  of  samples  should 
reach  depends  not  only  upon  the  nature  of  the  soil,  but  also  upon  that  of 
the  crop  expected  to  be  planted.  The  tap-root  of  a  pear  tree  will  in 
almost  any  soil  require,  for  normal  development,  a  depth  of  six  feet  at 
least;  hence  pear  trees  should  never  be  planted  in  shallow  soil.  Almonds 
and  peaches,  on  the  other  hand,  will  be  content  with  half  that  depth,  if 
necessary,  provided  the  soil  be  rich  enough  and  the  supply  of  moisture 
adequate,  but  not  excessive. 


In  coarse,  gravelly  soils,  as  well  as  in  hard  adobe,  it  may  become 
necessary  to  use  the  pick  and  spade  (not  shovel)  to  dig  a  vertical  hole 
of  sufficient  width  and  depth  for  observation,  and  for  the  taking  of 
samples  to  be  examined.  In  digging  such  holes  the  same  rule  as  above 
given  for  the  post-hole  borings  should  be  observed. 

When,  after  careful  examination  of  the  soil  and  subsoil  as  described 
above,  doubt  remains  as  to  the  cause  of  any  difficulty  observed,  or  when 
for  special  reasons  a  more  thorough  examination  of  the  case  is  desirable 
or  necessary,  samples  representing  the  average  of  not  more  than  one  foot 
each  may  be  taken,  from  the  surface  down  to  such  depth  as  may  be 
thought  needful  in  each  case,  in  accordance  with  the  directions  given  be- 
low, for  transmission  to  the  Experiment  Station  at  Berkeley. 

Value  of  Soil  Examinations  and  Analyses. — It  is  necessary  to  refer 
here  to  some  erroneous  ideas  and  prejudices  regarding  the  practical  ap- 
plication of  the  results  obtained  from  soil  examination,  and  from  chem- 
ical soil  analysis  especially.  While  some  imagine  that  such  an  analysis 
can,  like  the  assay  of  a  mineral,  tell  them  just  what  the  soil  is  worth,  or 
what  it  needs  to  make  it  productive,  others  have,  on  the  contrary,  been 
taught  to  believe  that  chemical  soil  analysis  is  utterly  useless,  and  can 
convey  no  information  useful  to  the  farmer.  As  usual,  the  truth  lies  be- 
tween the  two  extremes. 

The  physical  (mechanical)  and  chemical  conditions  existing  in  a  soil 
are  of  equal  importance  for  plant  growth;  if  either  be  seriously  defective 
the  farmer  will  labor  under  a  great  disadvantage.  But  usually  the  chem- 
ical deficiencies  are  more  readily  remedied  by  fertilization  than  physical 
defects,  which  should,  therefore,  receive  the  first  investigation  and  con- 
sideration. 

But  when  the  physical  conditions  are  found  satisfactory,  chemical 
analysis  will,  in  virgin  soils,  or  in  such  as  have  been  under  cultivation 
only  a  short  time,  give  most  definite  and  practically  useful  information 
as  to  the  means  of  improvement,  if  such  be  necessary.  The  habit  of 
many  Eastern  immigrants,  of  asking  how  to  fertilize,  right  at  first,  the 
exuberantly  fertile  natural  soils  of  California  and  of  the  arid  region  gen- 
erally, is  a  solicitude  wholly  uncalled  for.  The  farmer  cannot,  however, 
make  chemical  analyses  himself;  and  even  if  made  by  a  chemist,  they 
may  be  of  little  use  unless  the  method  employed  be  known  and  consid- 
ered, and  the  results  intelligently  interpreted  by  an  expert.  This  in  the 
case  of  soils  long  cultivated  and  fertilized  is  often  a  very  difficult  prob- 
lem, to  be  successfully  handled  only  when  the  cultural  history  of  the  soil 
area  in  question  is  known.  Hence  the  disappointments  so  commonly  com- 
mented on  in  the  Eastern  States  and  in  Europe,  where  nearly  all  soils  have 
been  artificially  changed. 

With  a  knowledge  of  the  composition  of  a  virgin  soil  and  of  the  crops 
that  have  been  or  are  intended  to  be  grown  upon  it,  we  are  in  a  position 
to  give  to  the  farmer  forecasts  of  what  is  most  likely  to  benefit  his  soil 
most,  with  the  least  expense,  and  with  at  least  equal  probability  of  correct 
judgment  as  in  the  case  of  a  physician  prescribing  for  a  patient.  In  both 
cases  the  practical  test  is  the  final  one;  in  both,  random  experimenting  or 
quacks  may  hit  or  miss  the  mark. 


DIRECTIONS  FOR  TAKING  SOIL  SAMPLES. 

In  taking  soil  specimens  for  examination  by  the  Agricultural  Experi- 
ment Station  of  the  University,  the  following  directions  should  be  care- 
fully observed— always  bearing  in  mind  that  the  examination,  and  espe- 
cially the  analysis,  of  a  soil  is  a  long  and  tedious  operation,  which  can- 
not be  indefinitely  repeated. 

First.— When  ascertaining  the  respective  merits  of  new  lands,  do  not 
take  samples  at  random  from  any  points  on  the  land,  but  consider  what 
are  the  two  or  three  chief  varieties  of  soil  which,  with  their  intermixtures, 
make  up  the  cultivable  or  cultivated  area,  and  if  necessary,  sample  these, 
each  separately;  then  sample  the  particular  soil  on  which  you  desire  in- 
formation, noting  its  relation  to  these  typical  ones. 

Second.— As  a  rule  take  specimens  from  spots  that  have  not  been 
changed  from  their  original  condition  of  ' '  virgin  soils, ' '  e.g.,  not  from 
ground  frequently  trodden  over,  such  as  roadsides,  cattle-paths,  or  small 
pastures,  squirrel  holes,  stumps,  or  even  the  foot  of  trees,  or  spots  that 
have  been  washed  by  rains  or  streams,  so  as  to  have  experienced  a  not- 
able change,  and  not  be  a  fair  representative  of  their  kind. 

Thir cL  —  Observe  and  record  carefully  the  normal  vegetation,  trees, 
herbs,  grass,  etc.,  of  the  average  virgin  land;  avoid  spots  showing  un- 
usual growth,  whether  in  kind  or  in  quality,  as  such  are  likely  to  have 
received  some  animal  manure,  or  other  outside  addition. 

Fourth.— Always  take  specimens  from  more  than  one  spot  judged  to 
be  a  fair  representative  of  the  soil  intended  to  be  examined,  as  an  addi- 
tional guarantee  of  a  fair  average,  and  mix  thoroughly  the  earth  taken 
from  the  same  depths. 

Fifth. — After  selecting  a  proper  spot,  pull  up  the  plants  growing  on 
it,  and  sweep  off  the  surface  with  a  broom  or  brush  to  remove  half- 
decayed  vegetable  matter  not  forming  part  of  the  soil  as  yet.  Dig  or 
bore  a  vertical  hole,  like  a  post-hole,  removing  a  foot  in  depth,  and  note 
at  what  depth  a  change  of  tint  occurs.  In  the  humid  region,  or  in  humid 
lowlands  of  the  arid,  this  will  usually  happen  at  from  six  to  nine  inches 
from  the  surface,  and  a  sample  taken  to  that  depth  will  constitute  the 
"soil." 

In  California  and  the  arid  region  generally  very  commonly  no  change 
of  tint  occurs  within  the  first  foot,  sometimes  not  for  several  feet;  hence, 
especially  in  sandy  lands,  the  "soil"  sample  will  usually  be  taken  to 
that  depth,  so  as  to  represent  the  average  of  the  first  foot  from  the  sur- 
face down. 

Samples  taken  merely  from  the  surface,  or  from  the  bottom  of  a  hole, 
have  no  definite  meaning,  and  will  not  be  examined  or  reported  upon. 

Place  the  soil  sample  upon  a  cloth  (jute  bagging  should  not  be  used 
for  the  purpose,  as  its  fibers,  dust,  etc.,  become  intermixed  with  the  soil) 
or  paper,  break  it  up,  mix  thoroughly,  and  put  at  least  a  quart  of  it  in  a 
sack  or  package  properly  labeled  for  examination. 

This  specimen  will,  ordinarily,  constitute  the  "soil. "  Should  the 
change  of  color  occur  at  a  less  depth  than  six  inches,  the  fact  should  be 
noted,  but  the  specimen  taken  to  that  depth  nevertheless,  since  it  is  the 
least  to  which  rational  culture  can  be  supposed  to  reach. 


6 


In  this  way  take  a  sample  of  each  foot  separately  to  a  depth  of  at 
least  three  feet;  preferably  four  or  five;  especially  in  the  case  of  alkali 
soils,  or  suspected  hardpan. 

Sixth.— Whatever  lies  beneath  the  line  of  change,  or  below  the  mini- 
mum depth  of  six  inches,  will  constitute  the  "subsoil."  But  should  the 
change  of  color  occur  at  a  greater  depth  than  twelve  inches,  the  "soil" 
specimen  should  nevertheless  be  taken  to  the  depth  of  twelve  inches  only, 
which  is  the  limit  of  ordinary  tillage;  then  another  specimen  from  that 
depth  down  to  the  line  of  change,  and  then  the  subsoil  specimens  beneath 
that  line. 

The  depth  down  to  which  the  last  should  be  taken  -will  depend  on 
circumstances.  It  is  always  necessary  to  know  what  constitutes  the 
foundation  of  a  soil,  dowu  to  the  depth  of  three  feet  at  least,  since  the 
question  of  drainage,  resistance  to  drought,  root-penetration,  etc.,  will 
depend  essentially  upon  the  nature  of  the  substratum.  In  the  arid  re- 
gion, where  roots  frequently  penetrate  to  depths  of  ten  or  twelve  feet  or 
even  more,  it  is  frequently  necessary  to  at  least  probe  the  land  to  that 
depth,  or  deeper. 

The  specimens  should  be  taken  in  other  respects  precisely  like  that 
of  the  surface  soil,  each  to  represent  the  average  of  not  more  than  twelve 
inches.  Those  of  the  materials  lying  below  the  third  foot  from  the  sur- 
face may  sometimes  be  taken  at  some  ditch  or  other'  easily  accessible 
point,  and  if  possible  should  not  be  broken  up  like  the  other  specimens. 

If  there  is  hardpan  or  heavy  clay  present,  an  unbroken  lump  of  it  should 
be  sent,  for  much  depends  on  its  character. 

Seventh.— When  in  the  case  of  cultivated  lands  it  is  desired  to  ascer- 
tain the  cause  of  differences  in  the  behavior  or  success  of  a  crop  on 
different  portions  of  the  same  field  or  soil  area,  do  not  send  only  the  soil 
which  bears  unsatisfactory  growth,  but  also  the  one  bearing  normal,  good 
growth,  for  comparison.  In  all  such  cases  try  to  ascertain  by  your  own 
observations  whether  or  not  the  fault  is  simply  in  the  subsoil  or  sub- 
strata; in  which  case  a  sample  of  surface  soil  sent  for  examination  would 
be  of  little  use.  In  such  examinations  the  soil  probe  will  be  of  great 
service,  and  save  much  digging  or  boring. 

Eighth.  —  Specimens  of  alkali  or  salty  soils  should  preferably  be 
taken  toward  the  end  of  the  dry  season,  when  the  surface  layers  will 
contain  the  largest  amount  of  salts.  A  special  sample  of  the  first  six 
inches  should  in  that  case  be  taken  separately  by  means  of  a  post-hole 
auger,  and  then,  in  a  different  spot  close  by,  a  hole  four  feet  deep  should 
be  bored,  and  the  earth  from  the  entire  four-foot  column  intimately  mixed 
before  the  usual  quart  sample  is  taken.  Samples  of  the  plants  growing 
on  the  land  should  in  all  cases  be  included  in  the  package,  as  they  indi- 
cate very  closely  the  agricultural  character  of  the  land. 

All  samples  taken  while  the  land  is  wet  should  be  air-dried  before  send- 
ing; in  the  case  of  alkali  soils  this  is  absolutely  essential. 

Ninth. — All  peculiarities  of  the  soil  and  subsoil,  their  behavior  under 
tillage  and  cultivation  in  various  crops,  in  wet  and  dry  seasons,  their 
location,  position,  "lay,"  every  circumstance,  in  fact,  that  can  throw 
any  light  on  their  agricultural  qualities  or  peculiarities,  should  be  care- 


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fully  noted,  and  the  notes  sent  by  mail.  Without  such  notes,  specimens  can- 
not ordinarily  be  considered  as  justifying  the  amount  of  labor  involved  in 
their  examination.  Any  fault  found  with  the  behavior  of  the  land  in 
cultivation  or  crop-bearing  should  be  especially  mentioned  and  described. 

The  conditions  governing  crop-production  are  so  complex  that  even 
with  the  fullest  information  and  the  most  careful  work,  cases  are  found 
in  which  as  yet  the  best  experts  will  be»at  fault. 

Send  by  express,  prepaid,  to  ' '  Agricultural  Exj)eriment  Station,  Berkeley, 
California. ' ' 

Always  mark  the  name  and  postoffice  address  of  the  sender  on  the  box  or 
package,  and  on  each  package  contained  therein;  also  on  a  pencil-written 
label  inside  of  each  package.  The  Station  staff  cannot  undertake  to  re- 
label such  packages,  and  thus  avoid  the  mistakes  and  losses  liable  to  happen 
as  the  result  of  this  omission. 

It  should  be  distinctly  understood  that  samples  sent  for  examination 
must  take  their  place  and  turn  on  our  docket,  and  can  only  in  excep- 
tional cases  be  advanced  for  immediate  report.  Usually  such  requests 
come  in  by  scores  in  the  autumn  and  winter,  just  prior  to  planting  time, 
with  the  request  for  immediate  report.  This  cannot,  as  a  rule,  be  given; 
work  already  in  hand  must  have  precedence.  Persons  desiring  such  ex- 
amination should  not  wait  until  so  late  in  the  season,  if  they  wish  to 
make  use  of  the  results  for  tlit,  coming,  planting  season. 


